U.S. patent application number 13/833091 was filed with the patent office on 2014-01-16 for system and method for manufacturing asphalt products with recycled asphalt shingles.
This patent application is currently assigned to Owens Corning Intellectual Capital, LLC. The applicant listed for this patent is Owens Corning Intellectual Capital, LLC. Invention is credited to James E. Burkett, Michael R. Franzen, Barry Garriett Hornbacher, Anthony Kriech, Laurand H. Lewandowski, Christian Peregrine, David Charles Trumbore, Herb Wissel.
Application Number | 20140014000 13/833091 |
Document ID | / |
Family ID | 49912827 |
Filed Date | 2014-01-16 |
United States Patent
Application |
20140014000 |
Kind Code |
A1 |
Franzen; Michael R. ; et
al. |
January 16, 2014 |
SYSTEM AND METHOD FOR MANUFACTURING ASPHALT PRODUCTS WITH RECYCLED
ASPHALT SHINGLES
Abstract
A method for manufacturing a processed asphalt suspension is
provided. The method includes dry grinding shingle waste material
to a particle size of less than 1 cm, forming ground recycled
shingle material, introducing virgin asphalt into a heated slurry
tank and mixing the ground recycled shingle material with the
virgin asphalt in the heated slurry tank, forming a mixed asphalt
slurry, introducing the mixed asphalt slurry into a wet grinding
machine, and recovering a processed asphalt suspension comprising
particles having a size no greater than about 200 microns. Roofing
and paving products manufactured from the processed asphalt
suspension are also provided.
Inventors: |
Franzen; Michael R.;
(Lombard, IL) ; Trumbore; David Charles; (Chicago,
IL) ; Lewandowski; Laurand H.; (Newark, OH) ;
Wissel; Herb; (Indianapolis, IN) ; Burkett; James
E.; (Perrysburg, OH) ; Hornbacher; Barry
Garriett; (Toledo, OH) ; Peregrine; Christian;
(Indianapolis, IN) ; Kriech; Anthony;
(Indianapolis, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Owens Corning Intellectual Capital, LLC |
Toledo |
OH |
US |
|
|
Assignee: |
Owens Corning Intellectual Capital,
LLC
Toledo
OH
|
Family ID: |
49912827 |
Appl. No.: |
13/833091 |
Filed: |
March 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61671742 |
Jul 15, 2012 |
|
|
|
61728891 |
Nov 21, 2012 |
|
|
|
Current U.S.
Class: |
106/273.1 ;
241/16 |
Current CPC
Class: |
C08L 2555/34 20130101;
B02C 19/0056 20130101; C10C 3/007 20130101; C04B 26/006 20130101;
Y02A 30/30 20180101; E01C 7/22 20130101; C04B 2111/00586 20130101;
C04B 2111/0075 20130101; C08L 2555/22 20130101; C04B 26/26
20130101; C08L 95/00 20130101; E04D 1/20 20130101; C08L 2555/52
20130101; E04D 5/06 20130101 |
Class at
Publication: |
106/273.1 ;
241/16 |
International
Class: |
C08L 95/00 20060101
C08L095/00; B02C 19/00 20060101 B02C019/00 |
Claims
1. A method for manufacturing a processed asphalt suspension
composition comprising: dry grinding shingle waste material to a
particle size of less than 1 cm, forming ground recycled shingle
material; introducing virgin asphalt into a slurry tank heated to a
temperature between about 150-260.degree. C.; adding said ground
recycled shingle material to said heated slurry tank and mixing
said ground recycled shingle material with said virgin asphalt in
said heated slurry tank, forming a mixed asphalt slurry;
introducing said mixed asphalt slurry into a wet grinding machine;
and recovering a processed asphalt suspension comprising particles
having a size no greater than about 200 microns.
2. The method of claim 1, wherein said virgin asphalt is oxidized
prior to mixing with the ground recycled shingle material.
3. The method of claim 1, further including adding an antifoam
agent is added to said virgin asphalt prior to the addition of said
ground recycled shingle material.
4. The method of claim 1, wherein the wet grinding machine
comprises an attritor.
5. The method of claim 1, wherein said processed asphalt suspension
comprises particles having a size no greater than about 150
microns.
6. The method of claim 5, wherein said processed asphalt suspension
comprises particles having a size no greater than about 100
microns.
7. The method of claim 1, wherein 90% of the particles in the
processed asphalt suspension are smaller than 150 microns and 50%
of the particles are smaller than 50 microns.
8. The method of claim 1, wherein said particles comprise at least
one of granules, fillers, and fiberglass.
9. The method of claim 1, comprising combining together: 5-65 wt. %
of the ground recycled shingle component; and 35-95 wt. % of the
virgin asphalt component.
10. The method of claim 1, further including a step of
incorporating additives into said processed asphalt suspension.
11. The method of claim 1, wherein said mixed asphalt slurry
remains in said wet grinding mill until the ground recycled shingle
material is fully integrated in the virgin asphalt.
12. The method of claim 1, wherein said ground recycled shingle
material comprises a powder having no more than 3% moisture
content.
13. The method of claim 1, wherein said processed asphalt
suspension includes about 10-60% processed shingle material.
14. The method of claim 1, further including manufacturing a
roofing product incorporating said processed asphalt
suspension.
15. The method of claim 14, wherein said roofing products include
one or more of hot roofing adhesive, modified shingle adhesive,
asphalt shingles, modified bitumen membranes, asphalt coated glass
plies and base sheets, asphaltic protector board, organic roofing
felt, mastics, coatings, and sealants.
16. The method of claim 14, wherein said virgin asphalt composition
is selected according to the specific roofing product to be
manufactured.
17. The method of claim 1, further including adding an aggregate
material into the wet grinding machine and manufacturing a paving
product incorporating said processed asphalt suspension.
18. The method of claim 17, wherein said paving products include
one or more of hot mix asphalt paving applications, warm mix
asphalt, and cold mix asphalt.
19. The method of claim 17, wherein said virgin asphalt composition
is selected according to the specific paving product to be
manufactured.
20. A processed asphalt suspension comprising: a ground recycled
shingle component derived from recycled asphalt based roofing
materials; and a virgin asphalt component, wherein the ground
recycled shingle component comprises particles of the recycled
asphalt based roofing materials which have been reduced in size to
have an average particle size of less than about 200 microns.
21. The processed asphalt suspension of claim 20, wherein the
particles have an average particle size of less than about 150
microns.
22. The processed asphalt suspension of claim 21, wherein the
particles have an average particle size of less than about 100
microns.
23. The processed asphalt suspension of claim 20, wherein the
particles comprise at least one of granules, filler and
fiberglass.
24. The processed asphalt suspension of claim 20, wherein said
processed asphalt suspension provides improved durability to
asphalt compositions.
25. The processed asphalt suspension of claim 20, wherein said
processed asphalt suspension provides improved fatigue and
stiffness to asphalt pavements.
26. The processed asphalt suspension of claim 20, comprising: 5-65
wt. % of the ground recycled shingle component; and 35-95 wt. % of
the virgin asphalt component.
27. The processed asphalt suspension of claim 20, wherein 90% of
the particles in the processed asphalt suspension are smaller than
150 microns and 50% of the particles are smaller than 50
microns.
28. A roofing product comprising: a processed asphalt suspension
comprising: a ground recycled shingle component derived from
recycled asphalt based roofing materials; and a virgin asphalt
component, wherein the ground recycled shingle component comprises
particles of the recycled asphalt based roofing materials which
have been reduced in size to have an average particle size of less
than about 200 microns.
29. The roofing product of claim 28, wherein said processed asphalt
suspension provides improved durability and shelf-life to said
roofing product.
30. An asphalt paving composition comprising: a processed asphalt
suspension comprising: a ground recycled shingle component derived
from recycled asphalt based roofing materials; and a virgin asphalt
component, wherein the ground recycled shingle component; and an
aggregate material, wherein said processed asphalt suspension
comprises particles of the recycled asphalt based roofing materials
which have been reduced in size to have an average particle size of
less than about 200 microns.
31. The asphalt paving composition of claim 30, wherein said
processed asphalt suspension provides improved fatigue behavior and
dynamic modulus to said asphalt paving composition.
32. An asphalt pavement made from the asphalt paving composition of
claim 29.
Description
[0001] This non-provisional utility patent application claims
priority to and the benefits of U.S. Provisional Patent Application
Ser. No. 61/671,742 filed on Jul. 15, 2012 and to U.S. Provisional
Application No. 61/728,891, filed on Nov. 21, 2012, each entitled
System and Method for Manufacturing Roofing Products with Recycled
Asphalt Shingles. Each application is incorporated herein by
reference in its entirety.
BACKGROUND
[0002] The present invention relates generally to asphalt products,
including processed asphalt compositions, that include recycled
shingle material. More particularly the present invention relates
to methods and apparatuses for forming processed asphalt
suspensions, including mixing systems and process methods for
creating performance enhanced asphalt compositions used in asphalt
products.
[0003] Asphalt roofing shingles make up over two-thirds of the
residential roofing market for both new homes and roof
replacements. However, the high volume production of asphalt
shingles leads to the production of significant waste, not only
during the manufacture of the shingles, but also through removal
("tear-off") of used shingles. In fact, it is estimated that 11
million tons of shingle waste is produced each year and
approximately 10 million of these tons end up buried in landfills.
The waste generated from the asphalt roofing products is
concerning, since the shingles themselves do not degrade and stay
permanently in the landfill. This and the fact that there is
considerable raw material value in the shingles has resulted in
significant efforts in recycling all types of roofing materials for
a variety of purposes.
[0004] U.S. Pat. No. 5,848,755 to Zickell et al. discloses an
asphalt roofing material recycling system used to recycle asphalt
materials, such as asphalt shingles and tar paper that include
granules, fibers or other particles. The asphalt material is
simultaneously heated and milled in a heated milling apparatus,
such as a heated ball mill, to reduce the size of the asphalt
material granules in suspension in liquid asphalt.
[0005] U.S. Pat. No. 6,290,152 B1 to Zickell discloses that asphalt
material is simultaneously heated and milled in a heated milling
apparatus such as a heated ball mill. Excess moisture is removed
from the asphalt material by continuously venting the heated ball
mill apparatus.
[0006] U.S. Patent Application Publication No. 2010/0129667 to
Kalkanoglu et al. discloses roofing products that are made from
recycled roofing materials. The recycled roofing materials can be
processed in an attritor or other media mixer to reduce the size of
roofing granules and fibers.
BRIEF SUMMARY
[0007] The general inventive concepts are directed to a method for
manufacturing roofing products using a processed asphalt
suspension. The method includes pre-processing shingle waste
material by grinding the material to a first minimum size, forming
ground recycled shingle material. The preferred process for
preparing the shingles is to dry grind the waste shingles using
horizontal or vertical shaft impactors or hammer mills. This
minimizes moisture in the ground shingles and allows removal of
metallic particles. This ground recycled shingle from either of
these processes produces a particle less than 1 cm. The ground
recycled shingles are stored in a dry condition until further
processing to make a processed asphalt suspension. According to
some exemplary embodiments, the ground shingles are processed in a
vibratory screen deck or trommel screen to remove the granules and
metallic material before being used to make the processed asphalt
suspension.
[0008] The process of making the processed asphalt suspension may
begin with a heated slurry tank. The tank may be partially filled
with virgin asphalt with a preferred temperature between
150-260.degree. C. The virgin asphalt is manufactured to produce a
processed asphalt suspension with rheological properties
appropriate to the end use application. An antifoam agent is
optionally added to the top of the mixed virgin asphalt to prevent
excessive foaming of the ground shingles from trapped moisture. The
ground recycled shingle material may then be added to the slurry
tank, forming a mixed asphalt slurry. The ground recycled shingles
are added slowly to the slurry tank to control moisture released as
steam. The mixer is powerful enough to keep the asphalt material in
suspension as any residual trace amounts of water trapped in the
ground recycled shingle is released as steam in the vented tank and
until the slurry is pumped to the next step in the process. The
tank may also be heated to bring the mixed asphalt slurry to the
proper temperature of 150-260.degree. C. before pumping to the
attritor or ball mill. This embodiment of producing a completely
dry processed asphalt prevents foaming of the slurry in the
attritor or ball mill from even low (<0.5% moisture) levels of
water trapped in the shingles.
[0009] The mixed asphalt slurry may then be fed into a wet grinding
mill, such as an attritor or stirred vertical or horizontal ball
mill. This device reduces the size of mineral matter and
agglomerates, including granules or fiberglass, until 90% of the
mineral matter or agglomerates is less than about 150 micron in
size and 50% is less than about 50 micron in size. This sizing
minimizes settlement in transport and storage.
[0010] A wide range of virgin asphalts, including un-oxidized, air
rectified, and oxidized asphalts as well as asphalt oxidized in the
presence of catalyst or asphalts modified by waxes, oils or other
additives may be used and are discussed in more detail below. The
mixture should spend enough time in the wet grinding machine to not
only reduce the size of the mineral particles, but also to fully
incorporate the asphalt from the recycled ground shingle material
into the virgin asphalt, thereby getting full use of the recycled
asphalt as a processed asphalt suspension
[0011] The foregoing and other objects, features, and advantages of
the general inventive concepts will become more readily apparent
from a consideration of the detailed description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention will be described with reference to
the attached drawings which are given as non-limiting examples.
[0013] FIG. 1 is a schematic diagram of the processes of producing
the ground recycled shingle material and the processed asphalt
suspension according to one embodiment of the present
invention.
[0014] FIG. 2 is a schematic diagram of an exemplary attritor or
ball mill.
[0015] FIG. 3 illustrates a graphical regression analysis that
depicts the softening point of the exemplary roofing products made
with the processed asphalt suspensions compositions listed in Table
1.
[0016] FIG. 4 illustrates the unexpected beam fatigue properties
for the processed asphalt suspension in an asphalt concrete beam
after 100,000 cycles loading compared to a control pavement without
the processed asphalt suspension.
[0017] FIG. 5 illustrates the improved dynamic modulus (E*) for an
exemplary asphalt concrete mixture containing the processed asphalt
suspension in comparison to a straight virgin asphalt mixture.
[0018] FIG. 6 illustrates the viscosity of exemplary calcite
asphalt mixes.
[0019] FIG. 7 illustrates the viscosity of exemplary talc asphalt
mixes.
DETAILED DESCRIPTION
[0020] The present invention is directed to methods and apparatuses
for producing roofing or paving products using a processed asphalt
suspension composition. The present application uses asphalt
shingle material that is reduced down to a particle size fine
enough to effectively reuse the recycled shingle material. That is,
the granules in the asphalt shingles are removed, or they are
reduced to a mesh fine enough to be incorporated into newly
manufactured products, such as roofing or paving materials, without
encountering significant settling of the particles in the
manufacturing process, shipment or storage. In some exemplary
embodiments, the recycled ground shingle materials are used to
produce a processed asphalt suspension that combines virgin asphalt
material and recycled shingle material that is tailored to a
specific end use. The asphalt in the recycled ground shingle
material may be intimately mixed with specially formulated virgin
asphalt so that the recycled asphalt may be completely assimilated
into the asphalt phase and the final properties of the slurry are
optimal for a particular end use. In this application the term
"virgin asphalt" refers to asphalt that is not recycled. The
intimate mixing brings the aged asphalt back into a useful
state.
[0021] The term "processed asphalt suspension" refers to a mixture
of virgin asphalt and recycled shingles and optionally other
materials, such as, for example, oils, waxes, polymers, and/or fine
mineral fillers. The asphalt products produced may include any type
of asphalt product desired by one skilled in the art, including,
but not limited to roofing low slope or steep slope roofing
applications as well as paving asphalt binders. Such roofing
applications may include hot applied roofing adhesives, modified
shingle adhesives, modified bitumen membranes, asphalt coated glass
plies and base sheets, asphaltic overlayment protection boards,
organic roofing felts, roofing cements, cold adhesives, and
mastics. Paving asphalt applications include modified asphalt
binders for hot mix asphalt, warm mix asphalt and cold mix asphalt
used in constructing roads, parking lots, airfields, or walking
paths.
[0022] The processed asphalt suspension composition used to produce
the processed asphalt products in accordance with the present
invention may be formed through a process that blends one or more
recycled asphalt materials, such as roofing shingles, that were
recovered, such as from old torn off roofs, from manufacturing
waste, or both, with virgin asphalt. The virgin asphalts used in
this invention may include any variety of vacuum tower bottoms from
the distillation of petroleum crude oil and further solvent
de-asphalted residua made from those vacuum tower bottoms. Vacuum
tower bottoms from re-refining of crankcase oil may also be
used.
[0023] The virgin asphalts may be used in blends with each other,
or the asphalts and blends of asphalts may be oxidized to raise the
softening point, as determined according to ASTM D36, and lower the
penetration, as determined according to ASTM D5. Catalysts, such as
ferric chloride or any form of phosphoric acid, may be used in the
oxidation process. Waxes and oils from petroleum or non-petroleum
sources may also be incorporated into the virgin asphalt prior to
incorporating the virgin asphalt or after manufacturing the
processed asphalt suspension. In some exemplary embodiments, the
recycled roofing shingles have an asphalt content of from about 15
to 40%, with the remainder of the product being mineral and glass
mat or organic felt. Although the asphalt products of the subject
invention will be described herein as including ground recycled
asphalt shingles ("RAS") as the asphalt additive, it should be
appreciated that any asphalt additive may be used in addition to
RAS. The method for processing the virgin asphalt and additive
together unexpectedly results in enhanced characteristics in the
resulting modified asphalt for roofing materials with enhanced
durability. In addition, modified asphalt for paving materials,
such as binders, showing enhanced and unexpected fatigue properties
in the resulting pavement.
[0024] Asphalt shingles are generally composed of a filled asphalt
(which contains an oxidized roofing asphalt and mineral filler). In
some exemplary embodiments, the filler comprises calcium limestone
or dolomitic limestone fillers in a ratio of 65% filler 35% shingle
coating asphalt. This filled asphalt coats a mat made of materials,
such as fiberglass or fabric. On the coated mat, granules of
different colors may be placed to give the shingle appearance
desired by the homeowner. These colors may be achieved by baking a
ceramic coating on the granules, such as, for example, a coating
composed of basalt or granite. When the old shingles are removed
from the roof at the end of their usefulness they are often mixed
with other debris from the tear-off, such as wood, nails and metal
(gutters) that may be taken off the roof, as well as paper and
plastic from the new roofing shingles packaging which are being
placed back onto the roof. The mixed roofing materials from the
tear-off should be processed to remove debris before grinding the
shingle material.
[0025] The asphalt shingles may be ground in a wide variety of
different ways, such as, for example, horizontal or vertical impact
crushers. According to some exemplary embodiments, the method
includes dry processing and avoids any addition of water to the
process. The standard grinding process is a one-step process of
shredding, grinding or milling asphalt shingles and predominantly
generates particles less than 1 cm. In this process, metal
particles may be removed magnetically to minimize their presence.
According to some exemplary embodiments, the ground shingles from
this process break up into three basic particle sizes. The coarse
fraction from 1.0 cm to #8 sieve (2380 micron) is comprised
primarily of asphalt coated glass or fabric. This fraction is
generally the highest in asphalt content. The mid size fraction, #8
mesh (2380 micron) to #30 mesh (595 micron), is primarily ceramic
coated granules and is the lowest in asphalt content. The smallest
fraction is less than #30 mesh (595 micron) and is comprised
primarily of mineral filler and roofing asphalt. The ground
recycled shingles can be separated into three sizes at this point
using standard screening methods to fractionate the materials to
remove different components before further processing if desired.
This screening works best when moisture content is <3%.
[0026] FIG. 1 illustrates a schematic diagram of an exemplary
process of producing processed asphalt suspension according to one
embodiment of the invention. As shown in FIG. 1, after the shingle
material is ground, the ground or shredded recycled shingle
particles may be stored in a dry condition (i.e., <3% moisture),
such as under a roof, until used to make the processed asphalt
suspension. The process of making the processed asphalt suspension
may begin with a slurry tank as illustrated in FIG. 1. The slurry
tank may be partially filled with virgin asphalt and heated to a
temperature between 150-260.degree. C. The virgin asphalt is
manufactured to produce a finished processed asphalt suspension
with rheological properties tailored for the end use application
desired. An antifoam agent may optionally be added to the top of
the mixed virgin asphalt to control foaming of the shingles which
contain low levels of trapped moisture. According to some exemplary
embodiments, the recycled shingles are added slowly to the heated
slurry tank to control the rate of steam release from the asphalt
slurry of ground shingles and virgin asphalt. The tank agitation
should be effective enough to keep the mixed asphalt slurry in
suspension. The tank may be externally heated to prevent buildup on
the coils and abrasion from mineral matter while mixing the mixed
asphalt slurry. The heating also brings the mixed asphalt slurry to
the proper temperature of 150-260.degree. C. before pumping to the
attritor or ball mill. This process produces a completely dry mixed
asphalt slurry which prevents foaming of the asphalt in the
attritor or ball mill from even low (<0.5% moisture) levels of
water trapped in the shingles. Drying shingles is often challenging
since the shingles tend to agglomerate into large pieces as the
shingles are heated above the softening point of the asphalt,
making handling as a particulate material difficult.
[0027] The mixed asphalt slurry may be fed to a wet grinding mill,
such as an attritor or stirred vertical or horizontal ball mill.
The term "wet grinding" is defined herein as a grinding process
that includes a liquid asphalt component. In some exemplary
embodiments, the grinding mill reduces the size of mineral matter
including granules, fiberglass, or cellulosic fiber until about 90%
is less than 150 micron and about 50% is less than the 50 micron
size. This sizing minimizes settlement in transport and storage and
assures complete mixing of virgin asphalt and asphalt in the RAS,
forming a processed asphalt suspension.
[0028] The grinding of the virgin asphalt and RAS may be performed
with any wet milling/grinding machine generally known and used in
the art. In some embodiments, a grinding mill is used that contains
internally agitated grinding media. The grinding material may
comprise stirred balls, or otherwise shaped objects. One type of
wet grinding mill is an attritor, which consists of a vessel,
grinding media, and a mixing arm. The mixing arm may be rotated
which agitates the materials and grinding media within the vessel.
When the rotating arm is rotated at high speeds, the arm creates
mixing in the media, which causes shearing and impact forces on the
material inside the vessel. U.S. Pat. Nos. 5,464,163 to Zoz and
3,458,144 to Lessells et al. exemplify conventional attritors,
incorporated by reference herein. The attritor may be a continuous
attritor, wherein the virgin asphalt/RAS material continually moves
into and out of the attritor. The attritor not only thoroughly
mixes the RAS with the virgin asphalt, but also removes the outer
coating on some additive particles, such that during the size
reduction, internal components of the additive are exposed and
blended homogenously with the virgin asphalt.
[0029] One exemplary process for recycling shingles and making a
processed asphalt suspension is shown in FIG. 2. The attritor
includes a vessel 1 which has a heating jacket or other means to
heat the contents of the vessel 1 and a mixing bar 2. The attritor,
whether batch or continuous, is sized based on desired production
rate and the residence time needed for reduction of mineral size
and incorporation of the ground recycled shingle asphalt into the
virgin asphalt. The exemplary attritor in FIG. 2 is 400 liters in
size. In some exemplary embodiments, hot oil may be circulated
through a jacket on the vessel in order to keep the mixture at an
appropriate viscosity. The mixing bar 2 extends into the vessel
which, as depicted, includes a plurality of arms 3 extending
outwardly from a central rotatable shaft of the mixing bar 2. The
arms extend from different levels of the rotating shaft centered in
the vessel. The mixing bar may then be rotated at high speed (about
100 to 1500 rpm), creating shearing and impact forces on the RAS
material inside the vessel.
[0030] The vessel 1 may include grinding media 4 and, for purposes
of the present invention, the grinding media may be preheated
together with the mixing bar 2 and walls of the vessel 1. However,
other grinding media materials and/or grinding media sizes may be
used. The grinding material is agitated within the vessel, causing
the inorganic component of the RAS to be ground into very fine
particles, such that about 90% of the inorganic component is
smaller than 150 microns and about 50% is smaller than 50 microns.
Residence time in the attritor may be from about 5 to 10 minutes to
higher times depending on the desired properties of the slurry. The
final particle size may be tailored to a particular end use product
to provide the most valuable filler for the specific product.
[0031] In some exemplary embodiments, the resulting processed
asphalt suspension comprises very fine particles having a size no
greater than about 150 to 200 microns. In some exemplary
embodiments, the particles have a size no greater than about 100
microns, and particularly no greater than about 74 microns. Some
products may require smaller particles, such as products that have
unique rheological properties (i.e., mastics), or products that
require a processed asphalt suspension that can withstand storage,
shipping, and use at higher temperatures without significant
settling of the particles. In some exemplary embodiments, the
attritor system that creates the fine particles is a continuous
process, in that water-free RAS/asphalt can be continuously pumped
into the attritor and the resulting processed asphalt suspension
may be continuously pumped from the attritor into a holding tank.
The average residence time in the attritor will then be determined
by the attritor size and the pump rate. The holding tank may be
heated and may include an agitator or recirculation system
sufficient to keep the particles in suspension. Alternatively, the
processed asphalt suspension may be formed into a solid material by
pouring into containers or pelletizing and then shipped to be used
either cold or reheated.
[0032] In some embodiments, the asphalt comprising the RAS has a
softening point between 30 and 110.degree. C. In other exemplary
embodiments, the asphalt is from torn off aged shingles and has a
softening point of from 95 to 150.degree. C. because of oxidative
aging on the roof. The filler may comprise mineral granules,
calcium carbonate or dolomite filler, talc or sand back-dusting in
varying quantities depending on the source of the asphalt shingles.
The RAS may also contain either glass mat or organic felt which
have been reduced in size in the initial grinding process.
[0033] An exemplary embodiment includes the ability to further
process the ground recycled shingles into different size fractions.
This can be accomplished using vibratory screen decks to remove
granules from the ground shingles. The remaining ground shingle
fractions can be recombined to produce a ground recycled shingle
material with higher asphalt content and less abrasive granule
content. This low granule mixture reduces wear on mixing and
grinding equipment from the basaltic granules.
[0034] In some exemplary embodiments, the processing steps of the
present invention involve incorporating the ground RAS material
into molten virgin asphalt, such as, for example, vacuum tower
bottoms from petroleum distillation, oxidized vacuum tower bottoms,
paving asphalts, oxidized paving asphalts, solvent de-asphalting
residua, oxidized solvent de-asphalting residua, re-refined motor
oil bottoms or combinations of any of the above, and subjecting the
molten virgin asphalt and RAS to a combination of mixing and drying
before being ground in a wet grinding mill, for example an
attritor, to produce a processed asphalt suspension.
[0035] After the processed asphalt suspension has been produced,
other additives may be added, such as waxes, polymers, chemicals,
etc., such that the final product can be tailored "as needed" in
post-processing steps for a particular manufacturing process. Some
of these additives can also be added in prior processing steps.
EXAMPLES
Production of Processed Asphalt Suspension
[0036] There are three main components in the production of
processed asphalt suspension: processing of the RAS input material
(FIG. 1: 1-4, 9), mixing and processing the processed asphalt
suspension (FIG. 1: 5-7, 9), and storage of the processed asphalt
suspension (FIG. 1: 8). Each component of the process will be
described in the following example.
Processing of the Shingle Input Material
[0037] The quality of the shingle input material is critical to the
production of the processed asphalt suspension. Quality refers to
the amount of debris present, moisture content, and the size of the
RAS after grinding and processing.
[0038] Debris is defined as the non-shingle materials present due
to the tear off process (nails, flashing, wood, packaging for new
shingles, etc.). Debris present during the processing is
detrimental to the performance of the pumps, hoses, storage tanks,
and mills used during the processing; however, minor amounts of
debris, such as about 5% may be tolerated. Debris removal is
accomplished through the use of magnets placed over conveyer belts
in the grinding, sizing and slurry vessel addition processes (FIG.
1: 9) as well as hand sorting to remove wood, plastic, metal and
plastic gutter as well as flashing.
[0039] Moisture content of the material should generally be less
than about 3% to minimize foaming in the asphalt slurry vessel.
Tear off shingles are typically delivered to the input processing
site in open top roll off containers that are exposed to the
weather for some period of time (FIG. 1: 1). The tear off shingles
are dumped and placed under roof and sorted to remove debris. The
processed shingles are then further processed through a dry grinder
or vertical shaft impactor to reduce the size of the agglomerates
(FIG. 1: 2). Neither the dry grinder nor vertical shaft impactor
uses water and thus are termed dry grinders. Through this dry
grinding step RAS input material is reduced to a size less than 1
cm and moisture is further reduced (FIG. 1: 2). Low levels of
moisture (<3%) are important to the size separation step.
[0040] RAS input material in this example was further separated
into sizes. A vibratory screen deck (FIG. 1: 4) was used to
separate the material in the current example. Other separation
techniques may also be used. A trommel screen is an example of an
alternate separation technique. In this example, the material was
separated into three sizes: material retained above #8 sieve (2360
microns), material retained above #30 sieve (595 microns) but at
the same time smaller than #8 sieve (2360 microns), and material
smaller than #30 sieve (595 microns). This sizing is for this
example only and many other size splits may be selected as desired
for a particular application (FIG. 1: 4).
Mixing of the RAS Processed Asphalt Suspension
[0041] A heated slurry tank with vigorous agitation was used for
the RAS/asphalt slurry tank (FIG. 1: 6). The slurry tank was filled
to about 1/3 of its volume with heated virgin asphalt and agitated.
An antifoam agent was added to the virgin asphalt. Exemplary
antifoam agents and defoamers that may be used include those which
have been used in asphalt applications such as silicones. An equal
amount, by weight, of RAS input material (in this example below #30
sieve (595 microns)), was added to the tank. RAS input material was
added at a rate such that the base asphalt would not foam over the
tank. Foaming may occur due to remaining moisture in the RAS input
material. The RAS input material may always have some level of
moisture making the rate of addition to the slurry tank an
important safety issue, so venting is recommended. The rate of
addition also influences the temperature of the slurry. In the
present example, the slurry tank was kept at a temperature above
130.degree. C. in order to maintain a viscosity in which the
agitator can maintain operation. Once the modified asphalt slurry
was produced, the slurry was further agitated and heated to a
temperature of 180.degree. C.
Processing the Modified Asphalt Slurry to Make Processed Asphalt
Suspension
[0042] The RAS slurry was further processed through an agitated
ball mill such as an attritor (FIG. 1: 7). In this example, a 400
liter attritor, with a 50 HP motor, was used. The operating
capacity of the attritor was approximately 265 liters of asphalt
slurried material. The asphalt slurry material was pumped from the
slurry tank to the attritor. All lines involved in the system may
be hot oil heat traced and insulated. The process for this example
was batch, although a continuous process may also be used. The
attritor was run for 10 minutes per batch. The attritor shaft speed
was 109 rpm, which translates to a tip speed of 4.5 meters/second.
After the material was processed in the attritor for 10 minutes it
was then pumped into the third component of the system, a storage
tank (FIG. 1:8). The batch capacity and attrition time were chosen
to create a processed asphalt suspension with an average particle
size of 50 microns or less. The average particle size for the
processed asphalt suspension created in this example was 32
microns.
Processed Asphalt Suspension
[0043] The resulting processed asphalt suspension may be used for
many products in the asphalt roofing and asphalt paving industries.
Virgin asphalt and RAS input materials can be combined in different
formulations to create desired properties of the final processed
asphalt suspension. In the current example, the processed asphalt
suspension was formulated to produce an end product with a specific
softening point and needle penetration range. During the processing
stage, batch formulations were changed by adding more or less
virgin asphalt and RAS input material to produce the desired
product results. The 19 batches were placed in a finished tank
(FIG. 1:8) with an average softening point of 96.degree. C. and
penetration of 14 dmm.
Storage of the Processed Asphalt Suspension
[0044] The processed asphalt suspension should be stored properly
to avoid settlement of the filler over long periods of time.
Storage tanks may be externally heated with mild agitation (FIG.
1:8). It may be beneficial for tanks to be externally heated
because filler in the processed asphalt suspension will deposit on,
coat and insulate the internal coils. Filler coating the internal
coils causes them to less effectively transfer heat. Light mixing
of the processed asphalt suspension keeps filler particles in
suspension, providing a homogenous product. The tank was visually
inspected after pumping off the processed asphalt. No visible
filler was present on the bottom of the tank.
Full Asphalt Utilization and Aging Benefit in Roofing Products
[0045] To demonstrate the benefits of mixing recycling shingle
material with virgin asphalt, a range of asphalt shingle coating
formulations were prepared using aged tear off recycled shingle
material smaller than a 20 mesh screen (smaller than 0.033 inches
or 841 microns), virgin asphalts made by blowing a blend of
asphalts (vacuum tower bottoms made from distilling predominantly
Canadian crude oils) and a finely ground calcium carbonate filler.
The materials were mixed together at a temperature between 175 and
200.degree. C. in a high speed Ross Mixer to simulate the complete
incorporation of recycled and virgin materials in an attritor. The
recycled shingle material was added at 0, 15, and 30% levels of
virgin asphalt replacement, the virgin asphalt was blown to 88, 95,
and 102.degree. C. softening points, and the filler was added so
that the final mix had 64, 67 and 69% total inorganic filler
content. Softening point data from the resultant formulations in
the experimental design is listed below in Table 3.
TABLE-US-00001 TABLE 3 % Recycle in Set Coating Overall Virgin
Asphalt Final Coating Point (% recycle asphalt Filler Softening
Point Softening Point Number to virgin asphalt (%) (.degree. F.)
(.degree. F.) 1 15 64 190 235 2 15 69 190 238 3 0 64 215 241 4 30
69 190 256 5 30 64 190 247 6 0 69 190 224 7 15 67 203 245 8 30 64
215 270 9 0 69 215 250 10 0 64 190 213 11 15 64 215 248 12 30 69
215 270 13 15 69 215 263 14 15 67 203 247 15 0 64 215 239 16 15 69
190 238 17 15 64 190 229 18 15 69 215 261 19 0 69 190 225 20 15 64
215 249 21 30 64 190 244 22 30 69 215 275 23 30 69 190 258 24 0 64
190 216 25 0 69 215 248 26 30 64 215 265 27 30 69 193 242 28 30 64
193 232 29 15 69 193 224
[0046] FIG. 3 illustrates a regression analysis that depicts the
softening point of the final coating product made with the 29
formulations listed in Table 3, above. The regression analysis
presents a linear model with filler %, virgin asphalt softening
point, and recycled asphalt content as parameters. The linear
equation was as listed below and had an r.sup.2 of 98%, indicating
that all but 2% of the variation seen in final blend softening
point was explained by these three variables.
SP-63.1+0.853 Virgin asp SP+0.954 Recycle content+1.83 Total Filler
%
[0047] The linear nature of the blend softening point with recycled
content (also designated virgin asphalt replacement) indicates that
the asphalt in the tear-off shingle is essentially completely
incorporated into the virgin asphalt and fully utilized in
determining the final product softening point. If that were not the
case, the final product softening point would drop below the linear
trend line at the higher recycled content values.
[0048] Table 4, below, provides data taken to determine the impact
of recycled content on durability of the asphalt shingle coating.
At the two filler extremes of 64 and 69%, nearly identical product
properties were achieved by two formulations: 1) a formulation with
no recycled content that used 215.degree. F. (101.67.degree. C.)
softening point virgin asphalt, and 2) a formulation that dropped
the virgin asphalt softening point to 190.degree. F. (87.78.degree.
C.), but added enough recycled shingle material so that 30% of the
asphalt was from recycled shingle and 70% was from virgin asphalt.
Weathering tests were run per ASTM D4798 using an Atlas Xenon Arc
Weatherometer and the average of 4 panels was taken for each set
point. The weathering test determines the number of cycles (or
days) before product failure, which is determined by cracks in a
thin coating of the asphalt material that is subjected to
conditions of light, heat, and water exposure.
TABLE-US-00002 TABLE 4 Filled Coating Filled Coating Durability
Softening Point (average of 4) Set Point (.degree. F.) (cycles to
failure) 64% filler, 0 recycle, 240 196 215 SP virgin asphalt 64%
filler, 30% recycle, 245.5 227 190 SP virgin asphalt % diff 2% 16%
69% filler, 0 recycle, 249 193.5 215 SP virgin asphalt 69% filler,
30% recycle, 257 212.5 190 SP virgin asphalt % diff 3% 10%
[0049] As can be seen in Table 4, while the physical properties of
the each of the samples were closely matched (softening point
within 3%) at each set point, due to the intimate mixing and total
incorporation of the recycled asphalt with the lower softening
point virgin material, unexpectedly, the durability was higher in
both cases by 16 and 10%, which indicates that using the
combination of virgin and recycled asphalt to achieve the product
softening point is superior in durability to solely using a more
highly oxidized virgin asphalt.
[0050] Asphalt shingle coating is just used as an example of these
properties. Other end products made with these materials would also
benefit from both the intimate mixing and use of old and new
asphalt and the durability demonstrated by this example.
Example 2
[0051] In the following examples, processed asphalt suspension
compositions were prepared according to the following method. The
RAS was mixed with virgin asphalt in a wetting tank and then
transferred to a 400 liter jacketed attritor. The grinding media
used in the attritor were 1 cm chrome steel ball bearings. The
system was preheated to approximately 175.degree. C. prior to
adding the asphalt/RAS mixture. A nitrogen blanket was introduced
to prevent oxidation during attriting. The mixing bar was rotated
at about 100-150 rpm. The grinding media and the asphalt additive
mixture were then mixed for about 5-12 minutes. During this process
the grinding media provides shearing and impact forces, which
reduce the asphalt additive particle size.
[0052] The processed asphalt suspension produced by the present
invention is particularly useful for preparing roofing products. As
mentioned above, such roofing products may include, but are not
limited to, hot roofing adhesive, modified shingle adhesives,
modified bitumen membranes, asphalt coated glass plies and base
sheets, asphaltic protector board, organic roofing felt, mastics,
coatings, and sealants. Each different type of roofing product
requires that the production process steps be specifically tailored
to the product. Such tailored specifics include, for example, the
type and amount of virgin asphalt in the final product and the
final particle size of the asphalt filler material. The virgin
asphalt may be formulated by the user of the invention and the
final particle size is determined by both the initial grinding
operation and the choice of attritor operating parameters.
Exemplary roofing products are discussed in more detail below.
Hot-Applied Roofing Adhesives
[0053] One exemplary roofing product that may be produced using the
processed asphalt suspension described above includes hot applied
roofing adhesives, such as tile adhesives, fleece-backed membrane
adhesive, insulation adhesive, etc. The input virgin asphalt may be
selected to produce the desired adhesive and flow properties in the
final product after it has been fully mixed with the aged asphalt
in the tear-off asphalt shingles. It may also be selected to
produce an acceptable equiviscous temperature (EVT) allowing
quality rooftop application and safe kettle temperatures.
Particularly, the hot applied roofing adhesives may have an EVT of
less than about 250.degree. C. for mechanical spreaders and
232.degree. C. for mopping, which means that the viscosity is less
than about 75 cps at 250.degree. C. and less than about 125 cps at
232.degree. C. The lower the EVT, the fewer problems will be
encountered with asphalt fuming, safety issues, and the degradation
in asphalt properties, such as reduction in softening point and
viscosity, that can occur during high temperature storage or use.
In some exemplary embodiments, the particles in the suspension do
not settle in the package, transport or kettle stages. The finely
divided mineral strengthens the adhesive bond at a low cost. In
addition to the asphalt, other additives, such as waxes or oils may
be added to further adjust the EVT. In some exemplary embodiments,
the product may be sold in bulk or in typical BURA cartons. In
other exemplary embodiments, the product may be pelletized and
packaged for future use.
[0054] The processed asphalt suspension used to form hot applied
roofing adhesives typically has about 10 to 60% recycled shingle
material and may have an overall solids content of about 6% to 50%.
More particularly, the recycled shingle content may be about 40 to
60% and the overall solids content about 28 to 50%. The ability for
the processed asphalt suspension composition to avoid settling may
be tested according to a modification of the procedure set forth in
ASTM D7173, which provides the Standard Practice for Determining
the Separation Tendency of Polymer from Polymer Modified Asphalt.
According to the standard method, asphalt and polymer blends are
poured into cigar tubes and set vertically into an oven at about
162.degree. C. for 48 hours. The method then tests the polymer
content in the top and bottom thirds of the tube. To measure these
portions of the composition, the tubes were removed after heating
and frozen. The tubes were then cut into three equal-size portions
and the top and bottom thirds tested for softening point and
dynamic shear rheometer, as determined according to AASHTO
T315.
[0055] The modification used in these examples with the recycled
asphalt and virgin asphalt mixes was as follows. The processed
asphalt suspension was tested at appropriate temperatures (for
example 162.degree. C., 177.degree. C., 204.degree. C., 232.degree.
C., and 260.degree. C.) for 48 hours and then the softening point
was used as an indicator of inorganic filler content and was tested
on the top third and bottom third of the material to look for
separation of filler. At 204.degree. C. an acceptable sample shows
a difference in softening point of less than 5% from top to bottom.
At 232.degree. C. an acceptable sample shows a difference in
softening point from top to bottom of less than 10%.
[0056] As an example of a specific hot-mopped adhesive formulation:
50% of an ASTM D312 Type 2 BURA asphalt (SP 70.degree. C. to
80.degree. C., needle penetration (ASTM D5) run at 25.degree. C. 18
to 40 dmm) was attritted with 50% of aged recycled asphalt shingle
material that had been ground in the enhanced shredding process.
The resultant product had the following properties which are
consistent with much of the spec for a Type 4 BURA material.
Softening point was 104.degree. C., needle penetration run at
25.degree. C. was 14.5, mopping EVT was 232.degree. C.
Additionally, the separation was in the range given above as
acceptable.
Additive to Modified Bitumen Adhesive
[0057] Another exemplary roofing product that may be produced using
the processed asphalt suspension includes using it as an additive
to polymer modified bitumen adhesives, for example those used in
making asphalt shingles. According to some exemplary embodiments,
the modified asphalt may be sold in bulk or in packages to
manufacturers who would blend it with polymers and possibly other
materials, or the product could be manufactured by the processed
asphalt suspension producer. The styrene butadiene styrene block
polymer (SBS) may be used alone or in combination with other
polymers and additives, but other polymer systems may also be used.
The processed asphalt suspension brings the benefits of recycled
content, a fully incorporated filler which can improve bond
strengths, and reuse of a resource of asphalt to act as the
continuous phase in the adhesive.
[0058] In some exemplary embodiments, the processed asphalt
suspension used to produce the polymer modified adhesive may
include about 10 to 60% recycled shingle material and may have an
overall solids content of about 6 to 50%. Preferably, the processed
asphalt suspension includes about 40 to 60% recycled shingle
material and an overall solids content of 28 to 50%. The ability
for the processed asphalt suspension to avoid settling may be
tested according to the modification of ASTM D7173 described above.
In some exemplary embodiments, the processed asphalt suspension has
a softening point range from about 80.degree. C. to 90.degree.
C.
Additive to Polymer-Modified Bitumen Membrane
[0059] Other exemplary roofing products that may be produced using
the processed asphalt suspension composition includes using it as
an additive to polymer modified bitumen membranes, as all or part
of the overall asphalt, as all or part of a mixture used to
pre-coat the mat prior to final coating, or as all or part of an
adhesive added to make the product peel and stick. To produce the
aforesaid products, the processed asphalt suspension may be sold in
bulk to manufacturers of modified bitumen membranes. Such membranes
may include atactic polypropylene polymer (APP) or styrene
butadiene styrene block copolymer (SBS). The final product may be
applied on the roof with adhesives, hot asphalt, or torches, or the
product itself may be a peel and stick membrane. The processed
asphalt suspension may be tailored for incorporation into a
modified bitumen membrane by carefully selecting a virgin asphalt
material to provide the desired product properties, and by grinding
the inorganic portion of the recycled material to produce an
optimum filler size for the membrane. Issues with damage to glass
or polymer mats used in the product from hard filler may be avoided
because of the fineness of the filler and also by separation of
granules prior to manufacture of the processed asphalt suspension.
Additionally, much or all of the mineral filler used in the
modified bitumen membranes may be provided in the processed asphalt
suspension, thus potentially eliminating a processing step in the
membrane manufacture and thereby saving on energy and production
time. The processed asphalt suspension may be transported hot in
bulk trucks, which is benefited from the lack of product
settling.
[0060] The processed asphalt suspension used to produce a polymer
modified bitumen asphalt or asphalt additive may include about 10
to 60% recycled shingle material and may have an overall solids
content of about 6 to 50%. Particularly, the processed asphalt
suspension includes about 20 to 60% recycled shingle material and
an overall solids content of 15 to 50%. The ability for the
processed asphalt suspension to avoid settling may be tested
according to the modification of ASTM D7173 described above. In
some exemplary embodiments, the processed asphalt suspension has a
softening point range from about 38.degree. C. to 66.degree. C.
Additives for Asphalt Coated Plies or Base Sheets
[0061] Another exemplary roofing product produced using the subject
processed asphalt suspension composition includes additives for the
asphalt used in making asphalt coated plies or base sheets used in
low slope roofing. As with the modified bitumen discussed above,
the filler material may be included in the attritor with the
processed asphalt suspension, which creates a very fine filler. The
fineness of the filler in the processed asphalt suspension and
pre-incorporation in the asphalt enables the filler to be
incorporated into standard or enhanced roofing plies with cost
benefits and potentially product benefits, such as fire performance
and higher filler loadings due to the fineness of the particles in
the processed asphalt suspension. Additionally, as mentioned above,
the fineness of the particles may also protect the glass mat from
damage.
[0062] The processed asphalt suspension used to produce the asphalt
coating for roofing plies or base sheets may include 10 to 60%
recycled shingle material and may have an overall solids content of
about 6 to 50%. More specifically the processed asphalt suspension
may include 40 to 60% recycled shingle material and may have an
overall solids content of 28 to 50%. The ability for the processed
asphalt suspension to avoid settling may be tested according to the
modification indicated above of the procedure set forth in ASTM
D7173. In some exemplary embodiments, the processed asphalt
suspension has a softening point range from about 85.degree. C. to
102.degree. C. and a needle penetration at 25.degree. C. of from 10
to 20 dmm.
Roofing Cements, Cold Adhesives, and Mastics
[0063] In yet another exemplary embodiments, roofing products
produced using the processed asphalt suspension composition include
roofing cements, cold adhesives, and mastics. These products are
commonly produced from asphalt, solvent, filler, fibers and in some
cases polymers. The products may be packaged in pails and applied
at ambient temperature. In some exemplary embodiments, the products
are thixotropic in nature, which allows for easy application of the
products and also the ability for the products to remain in place,
once applied. The processed asphalt suspension provides asphalt,
filler, and fibers, which are all ingredients normally incorporated
in the products, at a low cost. The processed asphalt suspension
has the potential to supply part or all of the asphalt and filler
used in the system and would supplement the fibers needed.
Additionally, the ability to adjust the fineness of the processed
asphalt suspension particulate material may benefit the thixotropic
nature of the product.
[0064] The processed asphalt suspension used to produce roofing
cements, cold adhesives, and mastics may include about 10 to 60%
recycled shingle material and may have an overall solids content of
about 6 to 50%. More specifically, the processed asphalt suspension
may include about 40 to 60% recycled shingle material and may have
an overall solids content of 28 to 50%. The ability for the
processed asphalt suspension composition to avoid settling may be
tested as indicated above. The product may be sensitive to settling
in the storage and handling of the processed asphalt suspension,
although not in the final product. In some exemplary embodiments,
the processed asphalt suspension has an SP range from about
38.degree. C. to 66.degree. C., although in other cases higher
softening point slurries would be used depending on product
formulation.
Example 4
Hot Mix Asphalt Paving Applications
[0065] The processed asphalt suspension as described in this
present invention can additionally be used to create hot mix
asphalt (HMA) pavements. The RAS can be mixed into virgin asphalt
at levels between 5 and 65% of the total mixture. In one exemplary
embodiment, the processed asphalt suspension contains 50% PG 58-28
with vacuum tower bottoms and 50% RAS. The properties of the
processed asphalt suspension are shown in Table 5.
TABLE-US-00003 TABLE 5 50% PG 58-28 with vacuum tower bottoms
Description 50% RAS Softening Point, .degree. F. 135.5 24 hours
Separation Test, .degree. F. 0.5 48 hours Separation Test, .degree.
F. 2 25.degree. C. Penetration 42 Solubility in TCE, % Soluble
81.49 Brookfield Rotational Viscosity @300.degree. F., PaS 0.469
Brookfield Rotational Viscosity @325.degree. F., PaS 0.275
Brookfield Rotational Viscosity @350.degree. F., PaS 0.150 Original
Binder DSR, G*/sin (delta), 76.degree. C., Kpa 0.96 Original Binder
DSR Fail Temp, .degree. C. 75.6 Original Binder DSR Phase Angle
@76.degree. C. 86.7 RTFO Mass Loss, % -0.321 RTFO Binder DSR,
G*/sin (delta), 76.degree. C., Kpa 3.34 RTFO Binder DSR Fail Temp,
.degree. C. 79.6 PAV Dynamic Shear, G*sin (delta), 31.degree. C.,
Kpa 2955 Creep Stiffness, -12.degree. C., Mpa 225 m-value,
-12.degree. C. 0.285 Estimated PG PG 75-20 Actual PG PG 76-16
[0066] The data shown above in Table 5 shows complete mixing of the
virgin and RAS asphalt based on rheological data under AASHTO M320
Performance Graded Asphalt Binder Specifications (Superpave). The
24 and 48 hour separation tests using ASTM D7173 also shows
acceptably low separation from settling of filler. The processed
asphalt suspension was used in a 9.5 mm surface HMA design. The mix
design used fine recycled asphalt product (RAP) (25.1%), two coarse
dolomitic aggregates both with a maximum particle size of 9.5 mm.
Coarse aggregate #1 was 25.4% and coarse aggregate #2 was 31.5% of
the aggregate weight. A dolomitic stone sand was 16.5% of the
aggregate weight. The remaining 1.5% of the aggregate weight is
accounted for by the aggregate breakdown during production. The
processed asphalt suspension content for the HMA mix was 5.8%. The
mix design blend is shown in Table 6.
TABLE-US-00004 TABLE 6 Sieve Size Percent Passing 1/2 100.0 3/8
96.8 #4 66.7 #8 37.8 #16 24.5 #30 16.3 #50 10.7 #100 8.1 #200
7.1
[0067] Samples of the plant produced HMA mix were taken from one of
the trucks before delivery to the paving site. A control mix was
also produced using a similar aggregate structure and a virgin
paving grade binder. Both mixes were lab tested for beam fatigue
and dynamic modulus (E*). Beam fatigue testing was used to
determine how well an HMA performs under repeated traffic loads. If
the strain in the HMA is too high, or the stiffness is too low,
under repeated loading the pavement may develop fatigue cracking,
which will ultimately lead to the pavement raveling and the
pavement coming apart. Beam fatigue testing may be performed on lab
compacted slabs using either plant produced or lab made HMA. This
testing includes cutting several beams to 380 mm long.times.50 mm
thick.times.63 mm wide from one slab. The beams are then placed in
an environmentally controlled chamber. Loads at a specific
frequency are imparted at two points near the center of the beam,
while the ends of the beam remained fixed. The deflection is
measured at the center of the beam. Recording the deflection of the
beam allows for the strain to be calculated at a given load,
frequency, cycle number, and temperature. The HMA which
incorporated the modified asphalt unexpectedly outperformed the
control mix. FIG. 4 shows the initial stiffness and the stiffness
after 100,000 load cycles of fatigue testing at 20.degree. C. for
the mix containing the processed asphalt suspension and the
control.
[0068] Dynamic modulus is a measure of the strength and load
resistance of an HMA pavement. Axial dynamic modulus testing may be
performed on lab made specimens with plant made or lab made hot mix
asphalt. In one exemplary embodiment, plant or lab produced HMA was
compacted in a Superpave gyratory compactor. The compacted HMA was
cored and cut to produce a final test specimen that has a 100 mm
diameter and was 150 mm tall. Dynamic modulus testing may be
performed in a temperature controlled chamber because the
temperature of the test specimen during testing is critical when
reporting dynamic modulus values. A load was axially applied in a
haversine wave frequency until the specimen had been subjected to
100 microstrain. The frequency of the loading directly relates to
speed of traffic. The load required to impart 100 microstrain on
the specimen was recorded. Using the diameter of the specimen, the
load in pounds was converted to stress (kPa). Axial dynamic modulus
is defined as the stress divided by the strain at a specific
frequency and temperature. Dynamic moduli for the mix containing
the processed asphalt suspension and the control mix were measured
at a temperature of 30.degree. C. and a loading frequency of 10
Hz.
[0069] The results are illustrated in FIG. 5. As illustrated, the
processed asphalt suspension mix unexpectedly outperformed the
control mix. The performance results for the RAS modified asphalt
mix indicate that it will perform as well or better than standard
HMA pavements. The use of finely divided fillers provided in the
processed asphalt suspension mix show unexpected improvements in
both fatigue behavior and dynamic modulus. Both properties are
important for rut resistance and durability in pavement
systems.
Example 5
Lowered Viscosity
[0070] To demonstrate the viscosity lowering benefits of blends
where some of the filler comes from the recycled asphalt shingle,
two sets of mixes were prepared targeting the same filler levels
but with some of the filler coming from the processed asphalt
suspension and some of it coming from virgin materials. In these
examples, tear off shingles were initially ground to a maximum size
of about 450 microns and then attrited in a 50/50 blend with an
oxidized asphalt that had a softening point of 74.degree. C. The
resultant processed asphalt suspension had a maximum particle size
of 100 microns, an asphalt content of 62.5% and a filler content of
37.5%.
[0071] In the first set of mixes, the processed asphalt suspension
was blended with varying levels of an asphalt coating (oxidized
asphalt with softening point of 101.67.degree. C. (215.degree. F.))
and a virgin calcite filler. Each blend resulted in a filler
loading of 65% and an asphalt loading of 35%, but were obtained by
using different levels of filler from the processed asphalt
suspension. Table 7, below, shows the mix specifics and FIG. 6
illustrates the viscosity as measured by a capillary rheometer,
according to the methodology outlined in ASTM D3835. Clearly at the
same total filler content the mixes using the processed asphalt
suspension had significantly lower viscosity at all shear rates.
One possible explanation is that the improved wetting of the
recycled filler aids in reducing the viscosity.
TABLE-US-00005 TABLE 7 Calcite Asphalt Mixes Modified Asphalt Total
Total % Virgin % Virgin Virgin Slurry (lb) Asphalt filler Calcite
Recycled Asphalt Filler (62.5% asphalt Setpoint % % filler Filler
(lb) (lb) and 37.5% filler) SP #2 35.2% 64.8% 100% 0% 7.6 14 0 SP
#6 35.3% 64.7% 90% 10% 4.2 10 3 SP #7 35.3% 64.7% 80% 20% 2.6 10
6.8
[0072] In the second set of mixes, talc filler, coating asphalt,
and processed asphalt suspension were mixed at different ratios to
make mixes with 49% asphalt and 51% filler but with varying levels
of processed asphalt suspension in the mix. The mixes are shown in
Table 8, below, and the resultant viscosity of the mixes are shown
in FIG. 7. The results indicated that once again, the more
processed asphalt suspension used, the lower the viscosity. One
possible explanation is that the improved wetting of the recycled
filler aids in reducing the viscosity.
TABLE-US-00006 TABLE 8 Talc Asphalt Mixes Modified Asphalt Total
Total % Virgin % Virgin Virgin Slurry (lb) Asphalt filler Talc
Recycled Asphalt talc Filler (62.5% asphalt Setpoint % % filler
Filler (lb) (lb) and 37.5% filler) SP #1 48.7% 51.3% 100% 0% 7.6
8.0 0 SP #3 49.2% 50.8% 90% 10% 6.4 7.2 2.2 SP #4 50.2% 49.8% 73%
27% 4.6 6.0 5.8 SP #5 49.1% 50.9% 50% 50% 1.0 4.0 10.8
[0073] Although the present invention has been described with
reference to particular means, materials and embodiments, from the
foregoing description, one skilled in the art can easily ascertain
the essential characteristics of the present invention and various
changes and modifications can be made to adapt the various uses and
characteristics without departing from the spirit and scope of the
present invention as described above and set forth in the attached
claims.
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